Have your child bite in the normal "chewing" bite, and look at the teeth.

Any child should be examined by an orthodontist at age 7 or 8. But if you look at your child's teeth and see something that looks like these pictures, it becomes more important to call a specialist for an examination.

Click on the picture to enlarge. Then compare.

A. Open Bite
Some overlap of the front teeth (dentists call it overbite) is normal and desirable. No overlap at all is called open bite, and it represents a significant departure from normal development. See an orthodontist right away.

B. Excessive Over Bite
As stated some vertical overlap is OK. Too much may cause unusual development of the bite. If your child bites and you can't see the lower front teeth, that is too much overbite. Call a specialist.

C. Crossbite
The upper teeth should overlap the outside of all of the lower teeth. If the upper teeth are tucked inside the width of the lower teeth, that is called crossbite. Crossbite might make the jaw grow crooked, or damage the teeth. Do not wait and see what happens. This case is made for a specialist.

D. Excessive crowding or teeth erupting in the wrong place
It is normal for teeth to look a little untidy during the mixed dentition stage of development. Severe crowding and teeth erupting in the wrong spot (ectopic eruption) is not normal.

E. Excessive overjet
Overjet to an orthodontist is what you might call overbite. Yes, it is a little confusing. What ever you call it, It is normal for the upper front teeth to project a little bit past the lower front teeth. If it is excessive, and especially if the lips have to strain to cover up the teeth, you should see an orthodontist. This problem just gets worse as time goes by.

Check the informative website of The American Association of Orthodontists